The vascular field of medicine relates to the diagnosis, management and treatment of diseases effecting the arteries and veins. The normal anatomy of these vessels is complex—with numerous divisions leading into progressively smaller branches. The development of disease within these vessels often alters their caliber, flexibility, and direction. These vessel's lumens will frequently become severely stenotic and at times, obstructed, by the development of atherosclerotic plaques or dissections. These obstructions may lead to the formation of new collateral pathways that follow new routes around the obstructions to provide blood flow down-stream from the blockage.
In order to diagnose and treat many vascular diseases, it is necessary for a physician to perform a diagnostic or interventional angiogram. Angiograms are specialized X-rays requiring access into a vessel with some form of sheath, needle or guide that allows contrast dye to be injected into the vasculature while X-rays are obtained. The contrast dye illuminates the interior of the vessels and allows the physician to note the anatomy as well as narrowings, abnormalities and blockages within the vessels. At times, more selective angiograms are necessary to better delineate a particular area of concern or disease. In order to obtain access to these more selective areas, it is necessary to insert guidewires and guide catheters into the vessels.
These devices can be visualized externally by the use of continuous low-dose fluoroscopy as they are manipulated through the body's vascular system. Even in conditions of normal anatomy, the negotiation of this rather complex anatomy can be difficult, time-consuming and frustrating. With the addition of diseased vessels that are narrowed or obstructed, such negotiation is significantly more difficult, and at times, impossible.
In an attempt to improve the situation, there have been a multitude of guidewires designed to negotiate these complex anatomies. Several different guidewire designs exist, each with a variation in its shape, size or length. In order to negotiate the smaller blood vessels as well as to provide some standardization within the industry, most catheterization systems work with guidewire diameters of 0.035″ or less. (0.018″ and 0.014″ being the next most common sizes, but sizes extend down to as small as 0.010″)
All of these guidewires are manipulated through the vascular anatomy via a combination of axial and rotational movements. Most guidewires have a tip that is bent, shaped or biased off the centerline. As the guidewire is advanced through the vasculature, it can be rotated to orient its tip in a different direction to facilitate its movement through the complex anatomy.
Since these guidewires all have small diameters, a gloved user will often have difficulty successfully gripping the guidewire to facilitate the necessary movements. Additionally, many guidewires have surface coatings designed to decrease the coefficient of friction and make the guidewires more slippery. This further contributes to the difficulty of controlling these guidewires.
In order to improve the control of these guidewires, many types of control devices have been developed. These are often referred to as Controllers or Torquers. They typically consist of a gripping mechanism that can be temporarily attached to the guidewire and a body attached to the gripping mechanism that can be gripped by the user. The gripping mechanism and the body provide the user with a better grasp of the guidewire and often provide a mechanical advantage to improve the provider's ability to move the guidewire.
The vast majority of these control devices are placed on the guidewire by co-axially loading the device on the guidewire at its most proximal end and sliding the device along the wire until it is at the place of use by the provider. When the device is at the desired location, it then is activated by the user to grip the guidewire. As the guidewire is manipulated through the anatomy, the device can be repositioned by releasing the gripping mechanism and sliding the device along the guidewire. When the device is no longer required, it can be removed from the guidewire by sliding it axially off the guidewire from its proximal endpoint.
A problem with this typical end-loaded (also referred to as over-the-wire) type of design relates to the significant amount of moving contact with the guidewire. This excess amount of movement increases the possibility that the guidewire can be inadvertently moved resulting in loss of position, damage to a vessel or failure of a procedure. Additionally, this increased degree of motion creates wasted motion, increases procedure time and can increase user frustration.